Fuel of the Future: Alternative Energy and Green Hydrogen

Alternative energy is energy drawn from sources other than conventional fossil fuels: sources that can be replenished naturally, or that release far less carbon when used. For India, which imports about 88 percent of its oil and roughly half of its natural gas, alternative energy is not an environmental luxury. It is the hinge on which energy security, industrial competitiveness, and the net-zero by 2070 pledge all turn. That is why UPSC keeps returning to it, from ethanol blending to green hydrogen.

Why India cannot run on fossil fuels alone

Energy security is the assurance that a country can access the energy it needs, at prices it can afford, without being hostage to supply shocks. India fails that test on fossil fuels: it imports the overwhelming share of its crude oil and about half of its natural gas, so every geopolitical tremor in West Asia or spike in shipping lanes feeds straight into the import bill and inflation. Alternative energy attacks this vulnerability at its root by substituting imported fuel with domestic sun, wind, biomass, and water.

The second driver is climate commitment. Under the Panchamrit pledges announced at COP26, India committed to 500 GW of non-fossil capacity by 2030 and net-zero emissions by 2070. Net-zero is the state where the greenhouse gases a country emits are balanced by the gases it removes, so no net addition warms the atmosphere. Neither target is reachable by efficiency gains alone; both demand new fuels for sectors that electricity cannot easily reach.

The third driver is industrial. Steel, cement, fertilisers, shipping, and aviation are hard-to-abate sectors: industries where direct electrification is technically difficult or prohibitively expensive. A country that cracks clean fuels for these sectors early, as India is attempting with hydrogen, positions itself as a supplier rather than a buyer in the coming energy order.

Biofuels: India's first big alternative bet

Biofuels are renewable fuels derived from biological sources such as agricultural residues, non-edible oilseeds, and waste biomass. India has made them the spearhead of its alternative-energy push. In 2025 the country achieved E20, petrol blended with 20 percent ethanol, ahead of schedule, and emerged as the world's third-largest biofuel producer. The blending saved foreign exchange worth about Rs 85,000 crore while raising rural incomes.

The National Biofuel Policy recognises four generations of biofuels, and the generation matters because each answers a different criticism. 1G biofuels use edible feedstocks like sugarcane juice and grains; 2G uses non-edible crop residues and waste; 3G uses algae; 4G covers advanced synthetic biofuels. India's first 2G ethanol biorefinery at Panipat in Haryana, using indigenous technology, converts 2 lakh tonnes of paddy straw a year into about 3 crore litres of ethanol, cutting roughly 3 lakh tonnes of CO2 annually while giving farmers a market for stubble that would otherwise be burnt.

The honest caveat is the food-fuel conflict: the competition between growing crops for food and growing them for fuel. Meeting India's ethanol targets has required large quantities of sugarcane, maize, and rice, raising concerns about land use, water use, and the diversion of subsidised grain. The policy answer is to shift decisively toward 2G and 3G feedstocks, restrict grain-based ethanol to genuine surplus years, and build decentralised plants, like those under the SATAT scheme (Sustainable Alternative Towards Affordable Transportation), which turns dung and agri-waste into compressed biogas near villages.

Flex-fuel vehicles (FFVs) are vehicles whose engines are designed to run on petrol, on ethanol, or on any mixture of the two, from the standard E20 blend up to E85 or pure ethanol (E100). A fuel sensor reads the blend and the engine software adjusts automatically, so the driver never has to choose.

Why they matter. Blending in ordinary cars stalls near E20, because ethanol attacks some engine materials and carries less energy per litre. FFVs are built for high blends from the start, so they open a market for India's surplus ethanol, and for the farmers behind it, beyond the 20 per cent wall. Carmakers have showcased flex-fuel models in India, and E85 retailing for certified flex-fuel vehicles began at public-sector outlets in 2026.

Hydrogen: the lightest fuel in the universe

Hydrogen is the lightest and most abundant element in the universe, and as a fuel it has a remarkable property: when it is burned or used in a fuel cell, its only by-product is water. A kilogram of hydrogen also carries roughly three times the energy of a kilogram of petrol. The catch is that hydrogen barely exists free in nature; it must be manufactured, and how it is manufactured determines whether it is clean or dirty. The industry uses a colour code for this:

Only green hydrogen is truly clean, because both the electricity and the process are carbon-free. Everything in India's hydrogen policy is therefore about making green hydrogen cheap and abundant.

Green hydrogen: splitting water with sunlight

Electrolysis is the process of passing an electric current through water to split it into hydrogen and oxygen. Do it with solar or wind electricity and you get green hydrogen. The device that performs it at scale is the electrolyser, and India currently depends on imports for most electrolyser capacity. Closing that gap is the job of the SIGHT programme (Strategic Interventions for Green Hydrogen Transition), a financial incentive sub-scheme that subsidises domestic electrolyser manufacturing and green hydrogen production itself.

The challenges are physical and economic, and a mains answer must name them honestly. First, cost: green hydrogen currently costs about Rs 300 to 400 per kg in India, against a mission target of Rs 100 per kg by 2030. Second, water: producing a kilogram of hydrogen needs roughly 10 litres of demineralised water, a real constraint in water-stressed regions, though coastal plants can use desalinated seawater. Third, storage and transport: hydrogen is highly flammable, leaks easily, and needs high-pressure tanks or cryogenic liquefaction, with refuelling infrastructure still scarce.

The National Green Hydrogen Mission

The National Green Hydrogen Mission, approved by the Union Cabinet in January 2023 with an outlay of Rs 19,744 crore, is India's flagship bet on the fuel. Its headline target is at least 5 million metric tonnes (MMT) of annual green hydrogen production capacity by 2030, backed by about 125 GW of additional renewable energy capacity, over Rs 8 lakh crore in expected investment, and six lakh potential jobs. The largest slice of the outlay, Rs 17,490 crore, funds the SIGHT programme, with the rest earmarked for pilot projects and research.

How the mission is organised. Four arms carry it: SIGHT, the incentive scheme for domestic electrolyser manufacturing and green hydrogen production; green hydrogen hubs, where production, storage, use and export infrastructure sit together; SHIP, a public-private partnership for research, pilot projects and international collaboration; and a skill development programme to train the hydrogen workforce.

Implementation is port-anchored by design, because hydrogen's first big market is export. Green hydrogen hubs are being developed at V.O. Chidambaranar Port (Tuticorin), Deendayal Port (Kandla), and Paradip Port, while Hydrogen Valley innovation clusters at Jodhpur, Odisha, Pune, and Kerala integrate production, storage, and end use in one geography. Pilot projects already sanctioned cover hydrogen in steelmaking, 70 hydrogen-fuelled vehicles across 21 routes with 16 refuelling stations, and NTPC's green hydrogen microgrid at Simhadri and solar-hydrogen plant at Leh.

The strategic logic is worth stating plainly in a mains answer: with 5 MMT of green hydrogen, India can cut fossil-fuel imports worth about Rs 1 lakh crore by 2030, decarbonise fertiliser and refining (which today consume dirty grey hydrogen), and sell green steel and green ammonia to Europe and Japan, turning an energy vulnerability into an export industry.

Fuel cells: turning hydrogen into electricity

A hydrogen fuel cell is an electrochemical device that converts the chemical energy of hydrogen directly into electricity, producing only water and heat as by-products. The overall reaction is 2H2 + O2 giving 2H2O plus electricity and heat. Unlike a battery, which stores energy, a fuel cell generates it continuously as long as hydrogen is supplied, which is why it suits vehicles and backup power rather than phones.

Applications already run from the showroom to the battlefield. The Toyota Mirai and Hyundai Nexo are commercial hydrogen cars; Germany's Alstom Coradia iLint runs hydrogen trains; and the Indian Oil Corporation has trialled hydrogen buses in Delhi NCR. Fuel cells also back up hospitals and data centres and power remote equipment. Their advantages are zero tailpipe emissions, up to 60 percent conversion efficiency, and refuelling in minutes rather than hours. Their disadvantages mirror hydrogen's: expensive platinum-based catalysts, costly production, and almost no refuelling network yet.

Sodium-ion batteries: the storage story India can own

Clean energy needs storage, because the sun does not shine at night. A battery is a device that stores electrical energy as chemical energy and releases it on demand. India today depends on imported lithium for lithium-ion batteries (LIBs), the dominant rechargeable chemistry, and lithium is concentrated in a few geopolitically sensitive regions. Sodium-ion batteries (SIBs) are an emerging alternative that swaps lithium for sodium, which is abundant in common salt and available domestically.

The science is a mirror image of lithium-ion: during charging, sodium ions move from cathode to anode; during discharge they flow back, generating current. In 2025, scientists at the Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR) in Bengaluru reported a fast-charging, long-lasting sodium-ion battery using a NASICON-type cathode material, charging to 80 percent in about six minutes and surviving over 3,000 charge cycles. It is a laboratory breakthrough, not yet a product, but it shows why the chemistry matters for Atmanirbhar Bharat (self-reliant India) in energy storage.

The lithium-ion ledger. Lithium-ion batteries dominate storage because they combine high energy density, long cycle life and fast charging in one package. The debit side is concentration and cost: lithium, cobalt and nickel come from a handful of countries, mining them is water-intensive, and spent batteries need organised recycling, which the Battery Waste Management Rules, 2022 now mandate. That ledger is exactly why chemistries built on abundant sodium matter to India.

Sodium-ion will not replace lithium-ion in phones or long-range cars, where energy density rules. Its honest niche is stationary grid storage, short-range mobility, and rural electrification: exactly the segments where India needs cheap, safe, domestically sourced batteries most.

Way forward: the exam-ready synthesis

A strong mains answer on alternative energy organises itself around the energy trilemma: security (cutting import dependence), equity (affordable access for all), and sustainability (the net-zero pathway). Biofuels buy time and rural incomes but must move to non-food feedstocks; green hydrogen is the long-term prize for industry and exports but must first cross the cost and infrastructure valley; storage chemistries like sodium-ion decide whether renewables can actually replace coal around the clock. Cite the mission numbers, name the bottlenecks honestly, and close with sequencing: incentives for manufacturing (SIGHT), pilots for learning (valleys and hubs), and standards for safety.

Drinking the sea: desalination

Desalination is the process of removing dissolved salts from seawater, and in some cases from brackish inland water, mineralised groundwater and treated municipal wastewater. The context is stark: 71 per cent of Earth's surface is water, but only 3 per cent is fresh, and of that only about 0.06 per cent is easily accessible in lakes, rivers and shallow groundwater; the rest is locked in ice caps, glaciers, deep aquifers and swamps.

Indian research is pushing the frontier: IIT Bombay scientists have developed lotus-leaf-like solar evaporators for salt-water treatment, and hydrophobic graphene membranes can remove salt ions with high precision, their single-atom thickness allowing ultra-fast water transport while blocking contaminants. The hurdles are familiar: scaling, high energy consumption and the low output of simple solar stills. Done right, desalination advances SDG-6, clean water and sanitation, and builds resilience in climate-stressed coastal regions.

Storing the sun: the BESS story

A Battery Energy Storage System (BESS) stores electricity, especially from solar and wind, and releases it when demand is high or renewable supply dips, smoothing the intermittency that is renewables' biggest weakness.

India's first commercial utility-scale BESS went live in April 2025: a 20 MW / 40 MWh battery cluster at Kilokri village in South Delhi, built by BSES Rajdhani, charged from renewable power purchase agreements and able to supply four hours of power daily, two by day and two by night, bringing reliable round-the-clock electricity to over 12,000 low-income consumers.

The battery family is diversifying beyond lithium:

Electric vehicles are the demand engine pulling this technology forward: the 2023 mains question on EVs asked how they cut carbon emissions versus combustion vehicles, through zero tailpipe emissions and higher drivetrain efficiency, with the grid mix deciding the true footprint. On the policy side, BESS growth needs viability gap funding, time-of-day tariffs, tax incentives and clear long-term procurement and grid-integration rules.

Microbes that brew fuel

Microorganisms are becoming refineries. They convert organic matter into renewable fuels through biological processes, a sustainable alternative to fossil fuels that fits India's energy transition, and the 2023 mains question on the subject shows its exam weight.

Four mechanisms drive it all: fermentation (sugars to alcohol fuels); anaerobic digestion (organic waste to biogas without oxygen); photosynthetic processes (algae and cyanobacteria using sunlight and CO2); and lipid accumulation (microalgae storing oils that become biodiesel). India's instruments include the National Bio-Energy Programme (2022), the SATAT scheme promoting compressed biogas (CBG) plants, and algae-biofuel research at CSIR labs.

The efficiency frontier: perovskite, blue LEDs and AI

Perovskite solar cells (PSCs) are a new generation of solar cells that use perovskite-structured materials as the light-absorbing layer. The perovskite layer absorbs sunlight and generates electron-hole pairs; electrons migrate to an electron transport layer and holes to a hole transport layer, driving current through an external circuit. Tandem perovskite-silicon cells have crossed 33 per cent efficiency in research settings, they are cheaper to manufacture than silicon, light and flexible enough for plastic sheets and building materials, and they perform well under cloudy and diffuse light.

The blue LED is the quiet hero of energy efficiency: the 2014 Nobel Prize in Physics honoured the invention of the blue light-emitting diode, which, combined with red and green, made bright white LED lighting possible. White LEDs now light homes at a fraction of the energy of incandescent bulbs, and the 2021 mains question on the blue LED's everyday impact confirms its exam relevance.

AI is becoming the grid's brain: smart-grid management analyses real-time demand and supply to optimise distribution and prevent outages; renewable forecasting predicts solar irradiance and wind speeds for parks like Bhadla; predictive maintenance spots equipment faults before failure; and AI-driven energy management systems optimise lighting, HVAC and industrial processes by occupancy and usage.

Securing the inputs: the National Critical Mineral Mission

The National Critical Mineral Mission (NCMM) aims to cut import dependence and build self-reliance in the critical minerals that clean energy, high-tech manufacturing and national security all need. It covers the full value chain: exploration, mining, beneficiation, processing, recycling and recovery from end-of-life products, onshore and offshore.

• Whole-of-government approach: ministries, PSUs, private industry, startups and research institutions with fast-track approvals for critical mineral projects.
• Strategic stockpiling: national reserves of critical minerals to ride out global supply disruptions and geopolitical shocks.
• International resource security: support for Indian firms acquiring overseas mineral assets and partnerships with resource-rich countries.
• Processing and value addition: Critical Mineral Processing Parks and financial incentives for domestic refining.
• Recycling and circular economy: recovery of critical minerals from end-of-life products.

What is the difference between grey, blue, and green hydrogen?

The colours describe how hydrogen is made and how much carbon that releases. Grey hydrogen comes from natural gas reforming with high emissions; blue hydrogen is the same process with carbon capture added; green hydrogen is made by electrolysing water with renewable electricity, giving near-zero emissions. Only green hydrogen counts as clean fuel.

What is the National Green Hydrogen Mission's main target?

Approved in January 2023 with Rs 19,744 crore, the mission aims for at least 5 million metric tonnes of annual green hydrogen production capacity by 2030, plus 125 GW of new renewable capacity. It expects over Rs 8 lakh crore in investment and about six lakh jobs.

How does a hydrogen fuel cell differ from a battery?

A battery stores energy and releases it; a fuel cell generates electricity continuously from supplied hydrogen and oxygen, emitting only water. That is why fuel cells suit vehicles, trains, and backup power, where refuelling in minutes beats recharging for hours.

Why is sodium-ion battery research important for India?

India imports almost all its lithium, which is concentrated in a few countries. Sodium is abundant domestically, so sodium-ion batteries promise cheaper, safer, self-reliant storage for grid and short-range uses, directly serving the Atmanirbhar Bharat goal in clean energy.

Key Terms

• Alternative energy: Alternative energy refers to energy sources that can substitute for conventional fossil fuels, typically renewables such as solar, wind, hydro, geothermal, and biomass, along with carriers like green hydrogen. The term is used in climate and energy security debates where the goal is decarbonisation plus reduced import dependence. For India it is tied to the 500 GW non-fossil capacity target for 2030 and the National Green Hydrogen Mission. Example: Solar parks like Bhadla in Rajasthan and offshore wind plans illustrate alternative energy deployment, while green hydrogen is positioned for hard-to-electrify sectors like steel.
• energy security: Energy security is the uninterrupted availability of energy sources at an affordable price, sufficient to meet a country's economic and strategic needs. For India it is a central concern because of heavy dependence on imported crude oil and exposure to volatile global prices and geopolitical disruptions. Policy responses include diversifying import sources, building strategic petroleum reserves, expanding domestic exploration and accelerating renewables and alternative fuels. Example: India's strategic petroleum reserves at Visakhapatnam, Mangaluru and Padur, which stockpile crude oil as a buffer against supply disruptions.
• net-zero by 2070: Net-zero by 2070 is India's commitment, announced at COP26 in Glasgow in 2021, that its net greenhouse gas emissions will reach zero by 2070. As a developing economy with large energy needs, India chose a later date than the mid-century targets of developed countries, invoking equity and its low historical emissions. Interim Panchamrit goals, such as 500 GW of non-fossil power capacity by 2030, mark the path toward it. Example: India's Long-Term Low Emission Development Strategy submitted to the UNFCCC lays out sectoral pathways toward the 2070 target.
• PANCHAMRIT: Panchamrit is India's five-point climate action pledge announced by Prime Minister Narendra Modi at COP26 in Glasgow in 2021. Its elements are 500 GW of non-fossil capacity by 2030, 50 percent of energy from renewables by 2030, one billion tonnes of projected emissions cut by 2030, 45 percent lower carbon intensity from 2005 levels, and net zero by 2070. For UPSC, it is the centrepiece of environment and climate questions. Example: Announced at COP26, Glasgow, 1 November 2021
• net-zero: Net-zero describes a balance between the greenhouse gases released into the atmosphere and those removed from it, so that net additions to the atmosphere are zero. It is achieved by cutting emissions as deeply as possible and then offsetting the remainder through sinks such as forests or technologies like carbon capture and storage. Countries, companies, and cities adopt net-zero targets with a specified year to align with the Paris Agreement's temperature goals. Example: A country reaches net-zero when its remaining emissions are fully matched by verified removals, such as afforestation or direct air capture.
• hard-to-abate sectors: Hard-to-abate sectors are industries whose greenhouse gas emissions are very difficult to eliminate with current technology, because they need extremely high temperatures or involve chemical reactions that release CO2. Steel, cement, chemicals, fertilisers, aviation, and shipping are the classic examples. Cutting their emissions depends on new technologies such as green hydrogen, carbon capture, and alternative fuels. Example: Steelmaking, where green hydrogen can replace coal as the reducing agent in direct reduced iron production.
• Biofuels: Biofuels are liquid or gaseous fuels produced from biomass, such as ethanol from sugarcane or maize and biodiesel from non-edible oils like jatropha or used cooking oil. They are blended with petrol and diesel to reduce fossil fuel imports and greenhouse gas emissions, and India classifies them into generations based on feedstock, from food crops (first generation) to agricultural waste (second generation). The flagship programme is ethanol blending, with India achieving 20 percent ethanol blending in petrol (E20) in 2025. Example: India's E20 programme blends 20 percent ethanol, largely produced from sugarcane molasses and maize, into petrol to cut oil imports and emissions.
• E20: E20 is petrol blended with 20 percent ethanol, the centrepiece of India's ethanol-blending programme to cut crude-oil imports, lower vehicular emissions and give farmers an alternative market for surplus cane and grain. India achieved the E20 target in 2025, ahead of the original 2030 schedule, and became one of the world's largest ethanol producers. The policy is now shifting from food-based first-generation ethanol toward residue-based second-generation and algae-based third-generation biofuels to avoid food-versus-fuel concerns. Example: Most petrol sold at Indian pumps today is E20, with 20 percent ethanol mixed into the fuel.
• National Biofuel Policy: The National Biofuel Policy of 2018 provides the framework for promoting biofuels such as ethanol and biodiesel in India to reduce fossil fuel dependence and cut emissions. It encourages blending ethanol with petrol and biodiesel with diesel, and was amended in 2022 to advance the 20 percent ethanol blending target (E20) from 2030 to 2025-26. The policy also promotes second-generation biofuels from agricultural waste through viability-gap funding for new refineries. Example: India achieved 20 percent ethanol blending in petrol in 2025, five years ahead of the original schedule.
• 1G biofuels: First-generation biofuels made from food and feed crops such as sugarcane, maize and vegetable oils, typically through fermentation or transesterification. They are technologically simple but raise the food-versus-fuel debate because they divert agricultural produce from food use. Example: much of India's E20 petrol-blending milestone, achieved in 2025, was met using ethanol from sugarcane molasses and maize, both first-generation feedstocks. Example: Ethanol from sugarcane molasses and maize used to meet India's E20 blending target in 2025.
• 2G ethanol biorefinery: A refinery that produces second-generation ethanol from non-food lignocellulosic biomass such as paddy straw, bagasse and other agricultural residues, avoiding the food-versus-fuel conflict of first-generation ethanol. It uses advanced pre-treatment and enzymatic hydrolysis to unlock sugars from tough plant fibre. Example: India's first 2G ethanol biorefinery at Panipat in Haryana uses indigenous technology to convert 2 lakh tonnes of paddy straw a year into about 3 crore litres of ethanol. Example: India's first 2G ethanol biorefinery at Panipat converts 2 lakh tonnes of paddy straw a year into about 3 crore litres of ethanol.
• food-fuel conflict: The tension that arises when crops, agricultural land or water are diverted from food production to biofuel production. Expanding biofuel mandates can push up food prices, encourage deforestation for energy plantations and pit energy security against food security, a concern sharpened by the 2007-08 global food price crisis partly linked to corn ethanol. The conflict is managed through policies favouring second generation biofuels from crop residues and non-edible feedstocks over first generation food crop fuels. Example: Debate over India's ethanol blending target of 20 percent (E20), achieved in 2025, over whether sugarcane and maize diversion for ethanol affects food inflation and water use.
• SATAT scheme: The SATAT scheme is the Government of India's programme, launched in October 2018, to set up 5,000 compressed biogas plants producing 15 million tonnes of CBG per year. Entrepreneurs build the plants and supply CBG to public-sector oil marketing companies for sale as automotive and industrial fuel, with support such as priority-sector lending. Its goals include cutting fuel imports, reducing stubble burning, creating rural jobs and giving farmers extra income. Example: A CBG plant using cattle dung and press mud can earn revenue both from gas sales to oil companies and from fermented organic manure sold as fertiliser.
• Hydrogen: Hydrogen is the lightest and most abundant element in the universe, and a versatile energy carrier that can be burned or fed into fuel cells to generate electricity with water as the only by-product. It is colour-coded by production method: green hydrogen made by renewable-powered electrolysis of water is clean, while grey hydrogen from natural gas carries a heavy carbon footprint. Example: India's National Green Hydrogen Mission targets annual production of 5 million metric tonnes of green hydrogen by 2030.
• Grey hydrogen: Grey hydrogen is hydrogen produced from natural gas through steam methane reforming without any carbon capture, so the process releases large quantities of carbon dioxide, several tonnes of CO2 per tonne of hydrogen. It is currently the dominant and cheapest production route worldwide, but it offers no climate benefit. In the colour scheme, grey (unabated fossil) contrasts with blue hydrogen (fossil with carbon capture) and green hydrogen (renewable electrolysis). Example: Most of the hydrogen India uses today in refineries and fertiliser plants is grey hydrogen made from natural gas.
• Blue hydrogen: Hydrogen produced from natural gas through steam methane reforming, with the resulting carbon dioxide captured and stored underground instead of being released. Because its emissions are substantially lower than conventional grey hydrogen, it is treated as a transitional fuel on the road to fully green hydrogen. Critics note that some emissions and methane leakage remain, so it is cleaner than grey hydrogen but not zero-carbon. Example: Several Gulf and European projects pair natural-gas reforming with carbon capture to market blue hydrogen for refineries and fertiliser plants.
• green hydrogen: Green hydrogen is hydrogen produced by splitting water through electrolysis powered by renewable electricity from sources such as solar or wind, so the production process releases no carbon dioxide. It is the cleanest form of hydrogen, unlike grey hydrogen made from fossil fuels, which emits CO2. Because it can store renewable energy and replace fossil fuels in heavy industry, it is central to plans for deep decarbonisation. Example: India's National Green Hydrogen Mission, approved in January 2023 with an outlay of Rs 19,744 crore, targets at least 5 million metric tonnes of annual green hydrogen production capacity by 2030.
• Pink hydrogen: Pink hydrogen is hydrogen produced by splitting water through electrolysis powered by nuclear energy, either as electricity or process heat. Like green hydrogen it has near-zero operational carbon emissions, but its low-carbon credential rests on nuclear power rather than renewables; the colour label is an informal industry shorthand, not a regulatory standard. Example: A nuclear power plant running an electrolyser to make hydrogen for steel or fertiliser production is producing pink hydrogen.
• Turquoise hydrogen: Turquoise hydrogen is hydrogen produced by methane pyrolysis, splitting natural gas into hydrogen and solid carbon without releasing carbon dioxide. It sits between blue hydrogen (made with carbon capture) and green hydrogen (made by renewable-powered electrolysis) as a lower-emission route that avoids both CO2 venting and the need for CO2 storage. The economics hinge on finding markets for the solid carbon byproduct. Example: The solid carbon produced alongside the hydrogen, which can be sold as carbon black for tyres, batteries and industrial materials.
• Brown or black hydrogen: The most polluting grade of hydrogen, produced by gasifying coal (lignite is called brown coal, bituminous coal is black coal) without capturing the carbon dioxide released. It emits large quantities of CO2 and is the cheapest but dirtiest production route. UPSC contrasts it with grey hydrogen (gas, no capture), blue hydrogen (gas with capture) and green hydrogen (renewable electrolysis). Example: Hydrogen made from coal gasification in coal-rich regions is classified as brown or black hydrogen.
• Electrolysis: Electrolysis is the process of using direct electric current to drive a chemical reaction that would not occur spontaneously, splitting a compound into its elements or simpler substances. In the water electrolyser, electricity splits water into hydrogen at the cathode and oxygen at the anode. When the electricity comes from renewable sources, the hydrogen produced is called green hydrogen, the centrepiece of India's National Green Hydrogen Mission. Example: Green hydrogen plants make fuel by electrolysing water with solar or wind power, emitting no carbon in the production step.
• electrolyser: An electrolyser is a device that uses electricity to split water into hydrogen and oxygen through electrolysis. It is the core technology for producing green hydrogen when powered by renewable electricity, since the process then emits no carbon dioxide. Electrolyser cost and efficiency are the decisive factors in whether green hydrogen can compete with fossil-fuel-derived grey hydrogen for industry, transport and energy storage. Example: Solar-powered electrolysers producing green hydrogen for refineries and fertiliser plants under India's National Green Hydrogen Mission.
• SIGHT programme: The SIGHT programme (Strategic Interventions for Green Hydrogen Transition) is the financial incentive sub-scheme of the National Green Hydrogen Mission that subsidises domestic electrolyser manufacturing and green hydrogen production itself. It is the largest slice of the mission's Rs 19,744 crore outlay, with Rs 17,490 crore earmarked for it. The mission targets at least 5 million metric tonnes of annual green hydrogen production capacity by 2030, backed by about 125 GW of additional renewable capacity. Example: Incentive support for domestic electrolyser manufacturing capacity under SIGHT.
• National Green Hydrogen Mission: The National Green Hydrogen Mission is the Union Cabinet approved (January 2023) programme to make India a global hub for green hydrogen production, with an outlay of Rs 19,744 crore. It targets 5 million metric tonnes of annual green hydrogen capacity by 2030 through the SIGHT scheme, which incentives electrolyser manufacturing and green hydrogen production. It matters for UPSC as a GS-3 energy transition and decarbonisation topic, linking net zero 2070, export potential, and prelims facts on outlay and targets. Example: The SIGHT programme under the Mission auctioned incentives for electrolyser manufacturing capacity in 2024
• Green hydrogen hubs: Green hydrogen hubs are clusters where production, storage, consumption and export infrastructure for green hydrogen are co-located to achieve economies of scale. Under the National Green Hydrogen Mission, such hubs are being developed at major ports so that green hydrogen and its derivatives (ammonia, methanol) can be produced near renewable-energy sources and shipped directly to overseas markets. Identified locations include V.O. Chidambaranar Port (Tuticorin), Deendayal Port (Kandla) and Paradip Port. Example: The hub planned at Deendayal Port, Kandla, is meant to anchor India's export of green hydrogen and green ammonia.
• Hydrogen Valley: Hydrogen Valleys are regional innovation clusters that co-locate hydrogen production, storage and end use in one geography, so that supply and demand for the fuel grow together. Under the National Green Hydrogen Mission, India is developing such valleys at Jodhpur, Odisha, Pune and Kerala, complementing port-anchored green hydrogen hubs at Tuticorin, Kandla and Paradip. Example: The Hydrogen Valley clusters being developed at Jodhpur, Odisha, Pune and Kerala under the National Green Hydrogen Mission.
• hydrogen fuel cell: A hydrogen fuel cell is a device that generates electricity by combining hydrogen with oxygen in an electrochemical reaction, with water and heat as the only byproducts. Unlike a battery, which stores energy, a fuel cell keeps producing electricity as long as fuel is supplied. It offers a clean alternative to engines and generators wherever hydrogen is available. Example: Fuel cell electric buses and cars, which emit only water vapour from the tailpipe.
• Anode: An anode is the electrode of an electrochemical cell at which oxidation occurs, meaning it releases electrons into the external circuit. In a discharging battery it is the negative electrode, while in an electrolytic cell (such as during charging) the polarity reverses but oxidation still occurs at the anode. The concept is foundational to batteries, fuel cells, and electrolysis. Example: In a lithium-ion battery, the graphite anode releases lithium ions toward the cathode during discharge.
• Electrolyte: An electrolyte is a substance, usually dissolved in a solvent or in molten form, that conducts electricity because it contains mobile ions that carry charge between electrodes. Common electrolytes include acids, bases and salts in solution, and they are essential components of batteries, fuel cells and electrolysers. In an alkaline water electrolyser, for instance, a potassium hydroxide solution serves as the electrolyte that carries ions between the electrodes. Example: The sulphuric acid in a lead-acid car battery is the electrolyte that enables it to store and release charge.
• External circuit: In a hydrogen fuel cell, the external circuit is the electrical path connecting the anode and cathode outside the cell through which electrons flow. Hydrogen is split into protons and electrons at the anode; the protons pass through the electrolyte to the cathode while the electrons are forced through the external circuit, generating the electric current that powers devices. This flow of electrons is what makes the fuel cell a source of electricity rather than just heat. Example: Connecting a motor to the fuel cell's external circuit lets the electrons' flow drive the vehicle.
• Cathode: A cathode is the electrode at which reduction occurs, that is, where a substance gains electrons. In a galvanic cell like a battery it is the positive terminal, while in an electrolytic cell it is the negative terminal. Cathode materials largely determine a battery's energy density, cost and lifespan. Example: In a green hydrogen electrolyser, hydrogen gas is produced at the cathode while oxygen evolves at the anode; in lithium-ion batteries, lithium cobalt oxide is a common cathode material.
• Toyota Mirai: The Toyota Mirai is a hydrogen fuel-cell electric vehicle first launched by Toyota in 2014 that runs on compressed hydrogen and emits only water vapour from its tailpipe. It converts hydrogen into electricity in an onboard fuel cell to drive an electric motor, making it one of the flagship examples of hydrogen mobility worldwide. Its second generation, launched in 2020, offers a driving range of roughly 650 km on a full tank. Example: Japan's deployment of Mirai fleets for government and taxi use as a showcase of its hydrogen society strategy.
• Hyundai Nexo: The Hyundai Nexo is Hyundai's hydrogen fuel cell electric SUV, a production vehicle that generates electricity on board by combining hydrogen with oxygen, emitting only water vapour from the tailpipe. It illustrates the transport end-use of green hydrogen, alongside peers such as the Toyota Mirai and Germany's Alstom Coradia iLint hydrogen trains. Example: The Nexo is one of the first commercially sold hydrogen fuel cell cars in the world, showing the technology has moved from prototypes to showrooms.
• Alstom Coradia iLint: The Alstom Coradia iLint is the world's first hydrogen fuel-cell passenger train, built by the French manufacturer Alstom, which entered commercial service in Lower Saxony, Germany, in 2018. Its fuel cells convert hydrogen and oxygen into electricity, emitting only water vapour, and it can run about 1,000 km on a single tank, making it a zero-emission alternative to diesel on non-electrified lines. It is the global reference point for hydrogen rail technology. Example: India is pursuing its own hydrogen train programme, with Indian Railways planning hydrogen-powered trains as part of its net-zero and green transport push.
• platinum-based catalysts: Platinum-based catalysts use the metal platinum to speed up chemical reactions without being consumed in them. Platinum's surface readily adsorbs hydrogen and oxygen, making it the standard catalyst for fuel cells and automotive catalytic converters. Its high cost and scarcity drive research into platinum-alloy and platinum-free alternatives. Example: The proton-exchange-membrane fuel cells used in hydrogen vehicles, where platinum catalysts at the electrodes split hydrogen and combine it with oxygen to generate electricity.
• battery: A battery is a device that stores chemical energy and converts it into electrical energy on demand through electrochemical reactions. Primary batteries are single-use and non-rechargeable, while secondary batteries can be recharged many times, and modern lithium-ion secondary batteries dominate portable electronics, electric vehicles and grid-scale storage. Batteries are the linchpin of the energy transition and digital infrastructure, and India promotes domestic manufacturing through production-linked incentive schemes for advanced chemistry cells. Example: Lithium-ion battery packs power electric two-wheelers and store solar power for nighttime use.
• Atmanirbhar Bharat: Atmanirbhar Bharat (Self-Reliant India) is the economic programme announced by the Prime Minister in May 2020 in response to the COVID-19 pandemic, backed by a Rs 20 lakh crore package amounting to about 10 per cent of GDP. It rests on five pillars (economy, infrastructure, technology-driven systems, vibrant demography, and demand) and seeks self-reliance through domestic manufacturing, resilient supply chains, and reduced import dependence. Its flagship instruments are the Production Linked Incentive (PLI) schemes. Example: PLI schemes for mobile electronics, solar modules, and pharmaceuticals aim to make India a manufacturing hub and cut dependence on imports, particularly from China.
• energy trilemma: The energy trilemma is the World Energy Council's framework describing the three competing goals every energy system must balance: energy security (reliable supply), energy equity (affordable and accessible energy for all) and environmental sustainability (low-carbon, clean energy). Improving one dimension often strains another, so policymaking is an exercise in managing trade-offs rather than maximising a single goal. It is a standard analytical lens for evaluating national energy policies. Example: India expanding coal-based power for affordable, secure supply while simultaneously adding record renewable capacity to meet sustainability goals.
• Key takeaways: Key takeaways is a quick-revision summary box placed at the end of each article, listing the most exam-relevant points in a short numbered list. It distils definitions, dates, figures, provisions and examples into a form suited for last-minute revision before Prelims and Mains. Together with the article's practice questions, it turns every topic into a self-contained study unit.
• lithium-ion batteries (LIBs): Lithium-ion batteries are rechargeable batteries in which lithium ions shuttle between a graphite anode and a metal-oxide cathode through an electrolyte, storing energy as chemical energy and releasing it on demand. They combine high energy density, long cycle life and light weight, which is why they dominate smartphones, laptops, electric vehicles and grid storage. Their geography is a strategic concern: lithium mining and refining are concentrated in a few countries, making import dependence a risk. Example: India's push for domestic lithium-ion cell manufacturing under the PLI scheme for Advanced Chemistry Cells aims to cut dependence on imported cells for electric vehicles, a dependence sharpened by the discovery of lithium reserves in Jammu and Kashmir's Reasi district.
• Sodium-ion batteries (SIBs): Sodium-ion batteries are rechargeable batteries that use sodium ions instead of lithium ions to carry charge between electrodes. They are attracting attention because sodium is abundant and cheap (sourced from common salt) while lithium and cobalt are scarce and import-dependent, making SIBs a promising low-cost option for grid-scale energy storage and affordable electric vehicles. Their energy density is lower than lithium-ion batteries, so they are better suited to stationary storage than long-range EVs. Example: Reliance New Energy Solar's acquisition of Faradion, a UK-based sodium-ion battery technology company, signalling commercial interest in the technology for Indian manufacturing.
• Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR): The Jawaharlal Nehru Centre for Advanced Scientific Research is an autonomous multidisciplinary research institute at Jakkur, Bengaluru, set up by the Department of Science and Technology in 1989 to mark the birth centenary of Jawaharlal Nehru. Founded by Bharat Ratna laureate C. N. R. Rao, it is now a deemed university carrying out advanced research in chemistry, physics, materials science, engineering and biology. It has consistently ranked among India's top research institutions in the National Institutional Ranking Framework and the Nature Index. Example: JNCASR's research groups work on areas such as nanomaterials, energy storage and water purification, including low-cost arsenic and fluoride removal technologies developed for rural water supply.
• flex-fuel vehicle: A flex-fuel vehicle (FFV) is a vehicle whose engine can run on petrol, ethanol or any blend of the two, up to E85 or pure ethanol (E100), with a sensor and engine software that adjust automatically to the fuel mix. Example: E85, with roughly 85 per cent ethanol, is retailed only for certified flex-fuel vehicles because ordinary petrol cars are not designed for it.
• SHIP (Strategic Hydrogen Innovation Partnership): SHIP is the research and partnership arm of the National Green Hydrogen Mission, a public-private platform that funds hydrogen research and development, pilot projects and international collaboration. Example: Under SHIP, Indian institutes and companies work with foreign partners on electrolyser and fuel cell research.

Prelims practice

Test yourself with these prelims-style questions.